Hermetically sealed switch



June 4, 1957 EQBACHMAN EI'AL 2,794,389

HERMETICALLY SEALED SWITCH I Filed Nov. 20, 1953 IN EN 0R. Eu ene ac manF 00K 5. B o/fa y Frank B. HICKS Q @fmg m;

4 TTOFNEYS nite HERMETIQALLY SEALED SWITCH Application November 20,1953, Serial No. 393,392

1 Claim. (Cl. 200-168) The present invention relates to electricswitches and more particularly to certain new and useful improvements inhermetically sealed electric switching devices of the type particularlydesigned for use in high altitude aircraft.

Hermetically sealed electric switching devices are not broadly new andmany such devices have been designed and constructed for use in highaltitude aircraft where low temperatures will cause a condensation andicing problem which will adversely affect the operation of the deviceand the electrical contacts of the switch unit. In such devices a shaftis usually passed through or cooperates with a simple diaphragm orbellows in the wall of a casing in such a manner as to permit anelectrical switch mounted and hermetically sealed in the casing to beactuated by movement of the shaft externally of the casing and fiexionof the diaphragm or bellows.

Hermetically sealed electric switching devices of the above type havenot, however, proved generally satisfactory, particularly where theswitching device is subject to numerous and repeated actuations. Undersuch conditions the devices have encountered fatigue problems after arelatively small number of operations with the result that the flexiblebellows fails, breaking the hermetic seal provided thereby andpermitting the entry of moisture or dirt into the housing.

The above noted defect of the prior art is remedied in accordance withthe present invention wherein certain new and useful improvements areprovided in an hermetically sealed electric switching device of the typedescribed, which is of both simple and sturdy construction and isinexpensive to manufacture; and in which the electrical switching unitmay be continuously and repeatedly actuated externally of the casingwithout encountering fatigue problems in the hermetic sealing meansprovided for the actuating mechanism.

More specifically, the present invention contemplates the provision in ahermetically sealed electric switching device, including a casing havingan opening and an electric switch supported in the casing having acontact member and a movable member adapted to be moved into and out ofelectrical engagement with the contact member: of a novel actuatingmeans cooperating through the opening in the casing for operating theelectrical switch from the exterior of the casing and for hermeticallysealing the opening.

In accordance with the preferred embodiment of the invention, theoperating means comprises a rod having an inner portion which extendsthrough the opening in the casing in spaced relation with respectthereto. Means are provided for rockably mounting the rod in andhermetically sealing the opening including a flexible bellows carried bythe casing in surrounding relation with respect to a portion of the rodintermediate its end portions, one end of the bellows being secured tothe wall of the casing in surrounding relation to the opening, and theother end of the bellows having an aperture therein through which an endportion of the rod is secured. A non-fluid semirigid plastic material isprovided which is contained with- States Patent M in the bellows and isadapted to hermetically seal the bellows both with respect to the casingand the portion of the rod extending therethrough, and, further, incooperation with the bellows to provide a rockable pivot for the rod.The inner end of the rod is adapted, upon rocking movement of the rod inthe aperture located in the casing, to operate through an actuatingmeans the movable switch member to move the same into and out ofelectrical engagement with the electrical contact memher.

The above, as well as other novel features of the hermetically sealedelectric switching device, will be more readily understood from thefollowing description of the accompanying drawings illustrating theinvention in accordance with its preferred embodiment, in which drawmgs:

Figure 1 is a sectional view of a hermetically sealed electric switchingdevice showing the novel actuating and sealing means according to thepreferred embodiment of the invention;

Figure 2 is a top end view of the switching device shown in Figure 1;and

Figure 3 is a sectional view along line 3-3 of Figure 1.

As shown in Figure 1 of the drawings, the electric switching deviceincludes a casing, generally designated as 10, in which is mounted oneor more conventional electric switch units, generally designated as 11aand 11b, respectively. The upper wall of the casing is provided with anopening or aperture 12 through which extends the actuating mechanism,generally designated as 13, which serves both to operate the switchunits 11:: and 11b from the exterior of the casing and to sealhermetically the aperture 12.

In accordance with the preferred embodiment of the present inventionillustrated, the actuating mechanism 13 comprises a rod 14 extending inthe manner shown through the aperture 12 in spaced relation with respectto the walls thereof. The rod 14 is rockably mounted in the aperture 12by means of a flexible bellows 15 carried within the casing insurrounding relation with respect to the inner portion of the rod; oneend of the bellows 15 being secured, as at 16, by soldering or otherwiseto the inner wall of the casing 10 in surrounding relation to theaperture 12, and the other end of the bellows being provided with anopening or aperture 17. The rod 14 is shown as provided with a threadedend portion 18 of lesser diameter than the central portion of the rod,which end portion extends through the bellows opening 17 with theshoulder 19 abutting the inner side of the end wall 20 of the bellows15. Contained within the bellows is a non-liquid flexible plasticmaterial 20, such as rubber or a silicone compound, which is poured intothe bellows in liquid form and then sets to non-liquid form. It thusfills and hermetically seals the bellows 15 with respect to the rod 14and casing 10 and serves to provide, in cooperation with the bellows 15,a supporting means for the rod 14 in which there is no fixed physicalpivot but which is such that the rod may be rocked within the aperture12 as though the rod 14 were pivoted at approximately the point at whichit passes through the casing.

The actuating mechanism 13 preferably includes an operating member suchas lever 26 located exteriorly of the casing and secured at one end bymeans of the screw 27 to the outer end of the rod 14, and a switchactuating member such as lever 28 located within the housing 10 andsecured at one end to the threaded end portion 18 of the rod 14 by meansof the nut 29, said end of the actuating lever 28 being fixed in spacedrelation from the outer side of the end wall 20 of the bellows 15 bymeans of the washer 30. As will be observed from member 26 will causethe rod 14 to pivot at approximately the point where it passes throughthe casing 10, as described hereinbefore, and the actuating lever 28 tobe rocked to depress the plunger 31a of the switch unit 11a.

The electric switch unit or units to be operated by the actuating lever28 may be of any suitable type in which a movable member is adapted tobe moved into and out of electrical contact with a contact member. Asshown in Figure 1, the two electric switch units (11a and 11b,respectively) presently illustrated, are of the type generally referredto as double acting microswitches, requiring relatively small actuatingmovements for operation. Each of the switches includes a supportingframe or housing 32 secured to the back wall of the casing 10,stationary contact members 3333 and 34-34, a movable doubleactingresilient snap blade 35 adapted to engage at its end portions thestationary contact members 33-33 and 3434, respectively, an operatingplunger 31:; and 31b, and a spring 36 adapted to normally urge andmaintain the operating plunger and snap blade in the position shown. Aswill be observed, switch unit 11b is so positioned below switch unit 11athat downward movement of the plunger 31a of switch unit 11a will betransmitted directly to plunger 31b of switch unit 11b and the twoplungers 31a and 31b will, therefore, operate simultaneously uponrocking movement of the actuating lever 28 to effect an upward snappingaction of the snap blades 35 which breaks electrical contact betweencontact members 3333 and establishes electrical contact between contactmembers 3434.

As shown in Figures 2 and 3, the bottom of the casing is provided withinner and outer insulating plates 40 and 41 which serve to close thecasing and to provide a supporting means for the electrical terminals,generally designated as 42, the inner ends of which terminals areconnected by means of lead wires 43 to the stationary contact members3434 and 35-35 of the microswitches 11a and 11b, respectively. In orderto seal hermetrically the insulating plates with respect to the casingand the terminals 42, the lower edge portion of the casing 10 is tightlysecured to the outer insulating plate 40 by means of screws 44 and aresilient bushing 45 is provided between the inner end of each of theterminals 43 and the inner insulating plate 41. As will be observed,each of the terminals 42 is secured in the outer insulating plate .40 bymeans of their flange portion 46 which is engaged in a correspondingcircumferal groove located in the wall of the hole formed in the outerinsulating plate 40 for reception of the terminal 42.

As is apparent from the foregoing, the switching device according to thepreferred embodiment of the invention as described is of both simple andsturdy constrution and is distinguished by the fact that the switchunits 11a and 11b may be repeatedly actuated by movement of the rod 14externally of the casing without occasioning a failure in thehermetically sealing means provided for the actuating mechanism. If,after repeated actuation and flexing of the bellows 15, an openingshould develop in the wall of the bellows, the plastic materialcontained within the bellows will continue to provide a hermetic sealbetween the rod 14 and the casing 107 As will also be apparent, theplastic material 20 in cooperation with the bellows 15 provides asupporting means for the rod 14 in which there is no necessity for anyfixed physical pivot but which is such that the rod may be rocked withinthe aperture 12 as though the rod were pivoted at approximately thepoint at which it passes through the casing. The plastic material alsoserves to prevent any water or moisture from entering into the bellows15 where it might freeze or otherwise cause damage or trouble.

What is claimed is:

An hermetically sealed switch unit of the character described includinga casing forming an envelope from which air may be excluded; said casinghaving an end wall provided with an aperture, electrical switching meansmounted within said casing and having an actuating plunger, means foroperating said plunger from the exterior of said casing comprising a rodrockably carried by said casing and extending through said casingaperture, an operating arm fixed to said rod exteriorly of said casingand extending from said rod in such spaced relationship to the aperturedend wall of said casing as to constitute said wall a limit stop forarresting movement of said arm and rod in one direction, a switchactuating arm fixed to said rod interiorly of said casing; said switchactuating arm having the major portion of its length disposed parallelto the major portion of said operating arm and the end portion thereofremote from said rod disposed in contiguous relation with said switchplunger, and flexible means for maintaining an hermetic seal betweensaid rod and said casing where said rod extends through said casingaperture, comprising a flexible bellows carried by the interior of saidcasing wall in surrounding relation with respect to a portion of saidrod intermediate its end portions; one end of said bellows being securedto the interior of said casing wall in surrounding relation to saidaperture and the opposite end of said bellows having an opening throughwhich an end portion of said rod passes, and a non-fluid semi-rigidplastic material cast in situ within said bellows in contact with theinner wall thereof, with a portion of the interior wall of said casing,and with a portion of the surface of said rod.

References Cited in the file of this patent UNITED STATES PATENTS627,671 Kelly June 27, 1899 2,468,512 Riche Apr. 26, 1949 2,527,475Bates Oct. 24, 1950 2,532,000 West Nov. 28, 1950 2,650,964 Razdow Sept.1, 1953 2,677,741 Martin May 4, 1954

